我回答了这个question
这是代码：
import java.net.NetworkInterface;
import java.net.SocketException;
import java.util.Collections;
import java.util.HashSet;
import java.util.List;
import java.util.Set;
方法！
private String[] getHostAddresses() {
Set<String> HostAddresses = new HashSet<>();
try {
for (NetworkInterface ni : Collections.list(NetworkInterface.getNetworkInterfaces())) {
if (!ni.isLoopback() && ni.isUp() && ni.getHardwareAddress() != null) {
for (InterfaceAddress ia : ni.getInterfaceAddresses()) {
if (ia.getBroadcast() != null) { //If limited to IPV4
HostAddresses.add(ia.getAddress().getHostAddress());
}
}
}
}
} catch (SocketException e) { }
return HostAddresses.toArray(new String[0]);
}
现在我想基于使用Lambda Stream Java 8进行翻译。这是我的代码：
try {
Collections.list(NetworkInterface.getNetworkInterfaces())
.stream()
.filter(ni -> !ni.isLoopback()) //unreported exception SocketException; must be caught or declared to be thrown
.filter(ni -> ni.isUp()) //unreported exception SocketException; must be caught or declared to be thrown
.filter(ni -> ni.getHardwareAddress() != null) //unreported exception SocketException; must be caught or declared to be thrown
.flatMap(ni -> ni.getInterfaceAddresses().stream())
.filter(ia -> ia.getBroadcast() != null)
.forEach(ia -> HostAddresses.add(ia.getAddress().getHostAddress()));
} catch (SocketException e) {
System.out.println(e.getMessage());
}
但当我改为使用Try catch ...
try {
Collections.list(NetworkInterface.getNetworkInterfaces())
.stream()
.filter(ni -> { //incompatible types: bad return type in lambda expression missing return value
try {
!ni.isLoopback(); //not a statement cannot find symbol symbol: method isLoopback() location: variable ni of type T where T is a type-variable: T extends Object declared in interface Stream
} catch (SocketException ex) { //exception SocketException is never thrown in body of corresponding try statement
Logger.getLogger(JPanelServerClient.class.getName()).log(Level.SEVERE, null, ex);
}
})
.filter(ni -> ni.isUp())
.filter(ni -> ni.getHardwareAddress() != null)
.flatMap(ni -> ni.getInterfaceAddresses().stream())
.filter(ia -> ia.getBroadcast() != null)
.forEach(ia -> HostAddresses.add(ia.getAddress().getHostAddress()));
} catch (SocketException e) {
System.out.println(e.getMessage());
}
根据提示@ Jacob-G这解决问题（但他有理由“不是一切都必须起作用”）
try {
Collections.list(NetworkInterface.getNetworkInterfaces())
.stream()
.filter(ni -> {
try {
return !ni.isLoopback();
} catch (SocketException ex) {
System.out.println(ex.getMessage());
return false;
}
})
.filter(ni -> {
try {
return ni.isUp();
} catch (SocketException ex) {
System.out.println(ex.getMessage());
return false;
}
})
.filter(ni -> {
try {
return ni.getHardwareAddress() != null;
} catch (SocketException ex) {
System.out.println(ex.getMessage());
return false;
}
})
.flatMap(ni -> ni.getInterfaceAddresses().stream())
.filter(ia -> ia.getBroadcast() != null)
.forEach(ia -> HostAddresses.add(ia.getAddress().getHostAddress()));
} catch (SocketException e) {
System.out.println(e.getMessage());
}
我怎么翻译它（更简单）？我怎么翻译呢？
不幸的是，处理java流中的已检查异常很难看。您必须创建一个单独的函数，该函数使谓词（过滤器操作）捕获任何已检查的异常，将其重新抛出为运行时异常
由于缺乏想象力，请考虑以下两个您无法控制的函数（想想库或jdk的一部分）：
boolean isEven(int i) throws IOException {
return i % 2 == 0;
}
boolean isOdd(int i) throws IOException {
return i % 2 == 1;
}
Stream.of(1, 2, 3, 4, 5)
.filter(i -> isEven(i))// compilation error
.filter(i -> isOdd(i))// compilation error
.collect(Collectors.toList());
方法1：为两个函数中的每一个编写一个包装器方法并处理那里的异常：
boolean isEvenWrapper(int i){
try{
return isEven(i);
} catch (IOException ex){
throw new UnCheckedIOException(ex);
}
然后你的流看起来像：
Stream.of(1, 2, 3, 4, 5)
.filter(i -> isEvenWrapper(i))
.filter(i -> isOddWrapper(i)) //compiles and runs.
.collect(Collectors.toList());
方法2：如果我们有1或2个过滤函数，方法1很容易，但如果我们有更多的过滤函数，为每个throwable方法编写包装函数变得单调乏味。
我们需要为一个抛出异常的谓词创建一个功能接口。
@FunctionalInterface
public interface CheckedPredicate<T> {
boolean test(T t) throws Throwable;
}
另一个谓词或方法，它采用CheckedPredicate并安全地评估它。
public static <T> Predicate<T> uncheckedPredicate(CheckedPredicate<T> predicate) {
return t -> {
try {
return predicate.test(t);
} catch (Throwable x) {
throw new RuntimeException(x);
}
};
}
现在我们的流变成了，
Stream.of(1, 2, 3, 4, 5)
.filter(uncheckedPredicate(i -> isEven(i)))
.filter(uncheckedPredicate(i -> isOdd(i))) //compiles and runs.
.collect(Collectors.toList());